1. Field of the Invention
This invention is directed to a heat pump system and more particularly to a self-contained heat pump capable of heating potable water, air conditioning, heating and dehumidification.
2. Description of the Prior Art
Presently, a conventional heat pump involves the process of transferring heat from a low-temperature reservoir to a higher temperature reservoir, expending mechanical energy in the process. To accomplish the transfer of heat, a cycle of evaporation, compression, condensation and expansion is performed on a heat-transfer medium operating within the heat pump.
A temperature reservoir of the heat pump may include such varied external sources as the air, water, earth, solar energy, or waste heat. The selection of the external source of the temperature reservoir is dependent upon the prevailing climate, topography and performance characteristics desired from the heat pump. For example, air is plentiful and easily available but heat pump output capacity and efficiency decreases as the heating requirements increase and the outdoor temperature drops.
It will be appreciated that conventional heat pump units are designed to utilize the same components in the operation of the cooling cycle and heating cycle.
Operation of the heat pump in the heating cycle begins as the heat-transfer medium, usually refrigerant, enters a compressor as a vapor. The vapor is pressurized in the compressor resulting in an increase in temperature. The heated vapor then is transferred to a condenser, also known as a refrigerant-air heat exchanger, heat is then removed from the refrigerant and transferred to a cooler conditioned space. Here the vapor condenses as it is cooled by the conditioned space and leaves as a high pressure liquid. The liquid refrigerant then flows through a refrigerant-flow restrictor and into a low pressure area. The reduction in pressure causes the liquid to partially vaporize and drop in temperature. The low temperature liquid-vapor mixture then flows through an evaporator, also known as an external source-refrigerant heat exchanger, where heat is absorbed from the external source. The liquid-vapor refrigerant mixture evaporates into a vapor as heat is absorbed. Now as a vapor, the refrigerant is returned to the compressor and the heating cycle is repeated.
The heat pump may be adjusted from the heating cycle to the cooling cycle by the use of a reversing valve at the discharge of the compressor. By switching the direction of flow of refrigerant, the role of the evaporator and condenser are effectively reversed resulting in cool refrigerant flowing to the evaporator to absorb heat from the conditioned space.
To provide the added capability of potable water heating, conventional heat pumps typically incorporate an additional refrigerant-potable water heat exchanger. The additional heat exchanger is added between the compressor and reversing valve. With the potable water-refrigerant heat exchanger in this position, the highest temperature refrigerant is always provided to heat potable water.
The disadvantage of these types of heat pump systems are that water heating can occur only when the heat pump is operating in either the heating or cooling cycle. It will be appreciated that in most climates heating and cooling occur only half of the time during the course of a year. Therefore, if the heating and cooling requirements are satisfied, the heat pump is not operating and hot potable water is not being produced.
Another disadvantage of the previously-known heat pump systems with potable hot water capability is that the amount of heat available for heating the conditioned space is reduced when the heat pump must simultaneously provide potable hot water heating and conditioned space heating. Most of the heat available in the hot vapor refrigerant is absorbed by the potable hot water heating system. Therefore, to provide adequate potable hot water heating capability and conditioned space heating, the compressor unit must be oversized resulting in an inefficient heat pump unit.
It is an object of the present invention to provide a unitary, self-contained, efficient heat pump system with full-time potable hot water capability. It is another object of the present invention to provide an efficient heat pump system capable of heating potable water, air conditioning, heating and dehumidification. It is yet another object of the present invention to provide an efficient heat pump system incorporating new functional systems to allow for two stages of heating, two stages of air conditioning, dehumidification, and potable water heating.
Other objects and advantages of the invention will become more apparent during the course of the following description when taken in connection with the accompanying drawings.